Precision achieved as a function of spectral band for stars with a rotational velocity of v sin i = 5.0 km s^-1 and spectral types M0, M3, M6, and M9. The dashed line represents the theoretical limits imposed by condition 1, and the filled area represents the values within the limits set by conditions 2 (circles) and 3 (triangles); blue, green and red represent the results obtained for resolutions of 60 000, 80 000, and 100 000, respectively. The spectra were normalized to have a S/N of 100 per resolution element as measured at the center of the J band (see Sect. 2 for details).